Aluminum bubbling
09-26-10, 03:53 PM
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Aluminum bubbling
I have a 2005 Giant aluminum frame. A couple years ago I noticed some bubbling under the paint where the bottle cages screwed in. I sanded, primed and touched the area up. Now I am noticing, some bubbling under the paint where the rear break outer casing is rubbing the paint on the top tube. It seems to be spreading a little bit and seems to be surface paint trouble. IT is a powdery substance if I scrape it off. Is this just cosmetic? i just don't want to over-worry the situation.
09-26-10, 04:19 PM
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more than likely it's a case of poor prep before painting, I'd guess. The powdery stuff seems to indicate corrosion...but I don't know much about painting aluminum, so I might be making that up. I can't think of why a cable housing rubbing would cause bubbles UNDER the paint instead of wearing it off from the top down, though.
Cracks or chips in the paint can be the first sign of frame failure, because the metal flexes and the paint lets go. You should be able to spot that if you remove the paint, which you have to do anyway if you're going to touch it up. Normally that would occur in a high-stress area, and the middle of the down tube or seat tube, where the bottle cages go, isn't one. I'd keep an eye on it for awhile, and if it doesn't get worse, just check it occasionally.
Cracks or chips in the paint can be the first sign of frame failure, because the metal flexes and the paint lets go. You should be able to spot that if you remove the paint, which you have to do anyway if you're going to touch it up. Normally that would occur in a high-stress area, and the middle of the down tube or seat tube, where the bottle cages go, isn't one. I'd keep an eye on it for awhile, and if it doesn't get worse, just check it occasionally.
09-26-10, 04:23 PM
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This bubbling started at the rear of the top tube under the sticker several years ago. OVer 3 years it has spread a bit. I do not believe there to be cracks as this has happened on several spots on the frame. Is this something to worry about?
09-26-10, 04:37 PM
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when the frame was going into paint, not all of the oils were wiped off of the frame, and after a while, that starts making its way through the paint. Unless you really, really love your paint job, there is no problem.
